Various systems require electrical coupling between electrical devices disposed within a hermetically sealed enclosure and external devices. Oftentimes, such electrical coupling needs to withstand various environmental factors such that a conductive pathway or pathways from the external surface to within the enclosure remains stable. For example, implantable medical devices (IMDs), e.g., cardiac pacemakers, defibrillators, neurostimulators and drug pumps, which include electronic circuitry and battery elements, require an enclosure or housing to contain and hermetically seal these elements within a body of a patient. Many of these IMDs include one or more electrical feedthrough assemblies to provide electrical connection between the elements contained within the housing and components of the IMD external to the housing, for example, sensors and/or electrodes and/or lead wires mounted on an exterior surface of the housing, or electrical contacts housed within a connector header, which is mounted on the housing to provide coupling for one or more implantable leads, which typically carry one or more electrodes and/or one or more other types of physiological sensors. A physiological sensor, for example a pressure sensor, incorporated within a body of a lead may also require a hermetically sealed housing to contain electronic circuitry of the sensor and an electrical feedthrough assembly to provide an electrical connection between one or more lead wires, which extend within the implantable lead body, and the contained circuitry.
A feedthrough assembly typically includes one or more feedthrough pins that extend from an interior to an exterior of the housing through a ferrule. Each feedthrough pin is electrically isolated from the ferrule, and, for multipolar assemblies, from one another, by an insulator element, e.g., glass or ceramic, that is mounted within the ferrule and surrounds the feedthrough pin(s). Glass insulators are typically sealed directly to the pin(s) and to the ferrule, e.g., by heating the assembly to a temperature at which the glass wets the pin(s) and ferrule, while ceramic insulators are typically sealed to the pin(s) and to the ferrule by a braze joint. High temperatures are typically required to join corrosion-resistant conductive materials with corrosion-resistant insulative materials.